It is concerned with clutches of the type shown in U.S. application No. 4,413,382 where a rope passes through a clamping mechanism which includes holes in a plurality of pivotable members, in one attitude of which edges of the holes gripping the rope and in another attitude of which, closer alignment of the axes of the holes and the rope allowing passage of the rope.
Such rope clutches have had the disadvantage that, at high loads it is difficult or impossible to release the rope. To try to overcome this a fixed-pivot toggle mechanism could be used but this does not function well for ropes whose diameters are at an extreme of the working range of the device because the angle of the members in the one attitude will vary with the diameter of the rope and at some angles it would provide poor initial mechanical advantage for the release handle and/or throw excessive strain on that handle.